Dispose the Day by Sersi and Cylla
The Xander/Spike of this really appeals to me. More respect than friendship building, but it was the start of a good dynamic. I'm not sure if this link has the complete story, I just found it for this post so I haven't checked it, but I have it in pdf if you would like a copy then please just pm me your email address.
Even Demons Need Friends and sequel
A Friend in Need by slaymesoftly
I have a note that there is an s/x friendship element to this but I'm not sure if it is really a main feature of the story.
I may be able to think of more but I don't have time right now, I'll try to remember to pop back later.
